import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      appBar: AppBar(
        title: const Text("UnconstrainedBox Demo"),
        actions: const <Widget>[
          UnconstrainedBox(
            child: SizedBox(
              width: 20,
              height: 20,
              child: CircularProgressIndicator(
                strokeWidth: 3,
                valueColor: AlwaysStoppedAnimation(Colors.white70),
              ),
            ),
          ),
        ],
      ),
      body: null,
    ),
  ));
}
